Plural stage disc mill with back pressure control means for each stage



D 1958 1.. E. EBERHARDT ET AL 2,864,562

PLURAL STAGE DISC MILL WITH BACK PRESSURE CONTROL MEANS FOR EACH STAGE Filed May 20, 1955 INVEN TOR. LEE E. Easm-mnor "9,, "name D. WuoRuFF ij lwlw FIG.2

United States Patent O PLURAL STAGE DISC MILL WITH BACK PRES- SURE CONTROL MEANS FOR EACH STAGE Lee Eberhardt and Maurice D. Woodruff, Springfield,

Ohio, assignors to The Bauer Bros. Company, Springfield, Ohio, a corporation of Ohio Application May 20, 1953, Serial No. 356,248

6 Claims. (Cl. 241-160) This invention relates to disc mills, and particularly to mills for refining fibrous materials in the presence of an added or residual liquid.

The object of the invention is to improve the construction as well as the means and modeof operation of disc mills, whereby such mills may not only be economical to build, but will be more eflicient and satisfactory in use, uniform in operation, and having relatively few parts and be unlikely to get out of repair.

A further object of the invention is to conduct the refining process in an enclosed space, with a controlled rate of flow of the material being worked on.

Another object of the invention is to achieve flow control as described in connection with a double-pass mill wherein the material is subjected to successive refining steps.

A further object is to provide a generally new mill structure wherein flow control is made an integral part of a so-called double-disc refiner wherein a single rotating disc is used in a manner to provide sequential paths of attrition. v

A-further object of the invention is to embody a high degree of flexibility of results and performance in the mill, through the use of independently adjustable valve controls and grinding adjustment.

A further object of the invention is to provide disc mills having the advantageous structural features, the inherent meritorious characteristics and the mode of operation herein set forth, or their equivalents.

With the above primary and other incidental objects in view as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof, and the mode of operation, as hereinafter described or illustrated in the accompanying drawings, or their equivalents.

In the drawings, wherein is illustrated one, but obviously not necessarily the only form of embodiment of the invention,

Fig.1 is a view in side elevation of a mill in accordance with the'illustrated embodiment of the invention, being partlydiagrammatic in form and partly broken away to show the mill structure; and

Fig. 2 is a view in end elevation of the mill of Fig. 1.

Like parts are indicated by similar characters of reference throughout the several views.

Referring .to the drawings, a disc mill, pulp refiner or the like inaccordancewith the illustrated embodiment of the invention, comprises a base lhaving generally upright, marginal walls 11. At opposite ends of the base,

on the walls 11, are bearings 12 receiving a shaft 13, one end of which is adapted for connection with a suitable rotary turning means.

Keyed to the shaft 13, midway between the bearings 12 is a refiner disc 14 carrying a first set of grinding segments 15 on one side face thereof and another set of like grinding segments 16 on the opposite side face thereof. Mounted in cooperative relation with the disc 14, on one side thereof, is a relatively stationary plate 17 carrying segments 18 in complementary, cooperative relation to the segments 15. In similar relation tothe disc 14, on the opposite side thereof, is a plate 19 carrying segments 21 complementary to the segments 16. The disc 14 and plates 17 and 18 are in concentric relation and define a dual mill structure, with the disc 14 being common to both. As is understood, in mills of the present class the material for refining is admitted to the spaces between the disc 14 and the plates 17 and 19 centrally or adjacent to the axis of the disc and then works its way radially outward between the grinding segments and is discharged from the periphery of the disc-plate assembly.

The amount of work done on the material in the described paths of attrition, and its rate of movement through such paths, are in part determined by the clearance between the disc and the plates 17 and 19, or, more particularly, between the opposed grinding segments carried thereby. This clearance is variable, the plates 17 and 19 being attached to and supported by a set of screw shafts 22 and 23 respectively mounted in standards 24 and 25 on the walls 11. Portions of the shafts 22 and 23 are screw threaded and hand wheels 26 and 27 are mounted thereon, the construction and arrangement of parts being such that the plates 17 and 19 may be independently adjusted to approach more closely to the disc 14 or to withdraw therefrom.

In surrounding relation to the shaft 13, intermediate the bearings 12, are complementary housing elements 28 and 29. At their outer ends the elements 28 and 29 are closed on the shaft 13. At their inner ends such elements register with and are received in central openings in the plates 17 and 19. The housing element 28 has an inlet opening 31 near one end thereof and the housing element 29 has a similarly located but oppositely disposed inlet opening 32, the material for refining entering such openings and fiowing to and through the respective paths of attrition as described.

In bridging, surrounding relation to the housing elements 28 and 29 and in spaced, enclosing relation to the refining. elements 14, 17 and 19 is an annular housing 33, the sides of which are closed upon the respective housing elements 28 and 29. The periphery of the disc 14 makes a sealing engagement with a central rib 34 in the housing 33, thus dividing the housing 33 into separate chambers 35 and 36. The chambers have respective outlet openings 37 and 38.

The inlet 31 and the outlets 37 and 38 have respective valve devices 39, 41 and 42 installed thereon controlling the flow of the material into the housing element 28 and out of the chambers 35 and 36. The valve devices are identical and are here indicated in part diagrammatically. Thus each is shown to comprise an open ended fitting 43 which is mounted a bushing 44 in turn receiving a rotary valve 45. The bushing 44 and valve 45 have opposed pairs of openings 46 and 47 which are brought to full registry, part registry or out of registry by a relative turning motion of the valve. Any suit able means may be provided for operating the valve 45,'which it will thus be understood serves as a shut off means, to deny or to permit material fiow thereby and also serves as-a throttle to increase and reduce the size} Patented Dec. 16, 1958 the mill and that in passing between the disc and the plate 17 the material is reduced by a cutting and rubbing action of the segments 15 and 18.

The material thus acted on leaves the chamber .35 by way of opening 37 and valve device 41 and is conducted by way of the conduit 48 to inlet 32 and housing element 29. From housing element 29 the material passes radially outward between the disc 14 and plate 19 and discharges into the chamber 36, a further reduction of the material taking place as it flows between the segments 16 and 21. The refined material escapes from chamber 36 by way of outlet 38 and valve device 42 and is conducted from the mill in a suitable manner, as by a conduit 49.

The degree of refining is determined by the adjustment of the valve devices and by adjustment of the clearance between the disc 14 and plates 17 and 19, it being understood that the plates 17 and 19 are independently adjustable so that relatively different results can be achieved in the first and second passes through the mill, if desired.

By way of example, if the valve devices 41 and 42 are wide open, the material being refined will pass through the paths of attrition at a rate determined by the clearance adjustment of the plates 17 and 19 and by the setting of valve device 39. In this instance, therefore, the pulping rate is established by valve device 39 and the clearance adjustment.

Similarly, with valve device 39 and valve device '41 wide open, and valve device 42 being used for throttling, the rate of flow through the mill is substantially entirely a function of the setting of valve device 42. As the size of the opening controlled by device 42 is increased and reduced there is a corresponding decrease and increase in the amount of work done on the material within the grinding or attrition paths.

Further, with valve 39 and 42 in wide open position, and valve device 41 being used for throttling, the rate of flow between disc 14 and plate 17 is largely a function of the setting of the device 41 whereas there is a relatively free flow and discharge of the material beyond the valve device 41.

It will thus be seen that the present arrangement provides practically an unlimited range of control over the operation of the mill and the final characteristics of the material passed therethrough. With valves 41 and 42 closed or partly closed, the material will fill the milling chambers and the rate of flow through the machine will be a function of the valve opening. The lower the rate of flow, the longer the material remains in the milling zone and the greater is the amount of refining of the material. The rate of flow may be easily regulated in each individual chamber or in the two chambers conjointly by proper adjustment of either one or both of said valves. The quantity of material processed as well as the amount of refining done thereon may be accurately and easily controlled by proper balancing of flow rates through the chambers under control of the valves 39--41-42.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been describedin language more or less specific as to structural features, it is to be understood that the invention is not limited to the specific features shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect.

Having thus described our invention, we claim:

1. A disc mill, including a rotatable shaft, a rotary disc mounted on said shaft for rotation therewith and having grinding surfaces on its opposite sides, relatively stationary plates in opposing relation to the opposite sides of said disc, means for adjusting said plates to vary the clearance between said plates and the grinding surfaces on said disc, and means defining a flow passage for the material being refined directing the ma terial radially between said disc and one of said plates and then to the opposite side of said disc and radially between said disc and the other said plate.

2. A disc mill according to claim 1, characterized by valve means in said passage controlling the material flow to the said opposite side of said disc.

3. A disc mill according to claim 1, characterized by valve means controlling flow into said passage, other valve means controlling flow out of said passage and still other valve means controlling flow to the said opposite side of said disc.

4. A disc mill, including a rotatable disc, relatively stationary plates on the opposite sides of said disc defining therewith respective radial attrition paths, a housing assembly enclosing said disc and plates and defining independent inlets to said attrition paths, discharge chambers, and outlets from said discharge chambers, and a flow connection from the outlet from one attrition path to the inlet of the other.

5. A disc mill according to claim 4, characterized by valve means at the inlet to said one attrition path, other valve means at the outlet therefrom and still other valve means at the outlet from the other said attrition path.

6.A disc mill including first and second sets of relatively rotatable refining elements, means defining a closed flow passage between said sets of refining elements, means in said passage for regulating the rate of flow of material from one of said sets to the other, means defining an inlet to one of said sets for delivering material to be refined centrally thereof for radial dispersal therebetween to said closed flow passage and means defining an outlet from the other of said sets having means connected for producing a back pressure on the material flowing from said sets of refining elements whereby to control the quality of the material refined by controlling the period of refining intermediate said sets of refining elements.

References Cited in the file of this patent UNITED STATES PATENTS 1,624,037 Butler Apr. 12, 1927 1,807,808 Symons June 2, 1931 1,814,587 Daniels July 14, 1931 2,260,834 Everett Oct. 28, 1941 2,323,490 Scherlf July 6, 1943 2,591,106 Sutherland Apr. 1, 1952 FOREIGN PATENTS 99,120 Sweden Apr. 11, 1940 122,054 Switzerland Aug. 16, 1927 

